This invention relates to an adjustable platform mountable on a surface such as a boat hull for providing a mounting surface adjustable to a substantially horizontal orientation irrespective of the orientation of the surface on which the platform is mounted.
Controlled depth fishing is a method used by sport fishermen when trolling or still fishing to place a lure or bait at a fixed depth beneath the water surface where fish are expected to be found. The particular depth will vary with such factors as the type of fish, the season of the year, weather conditions, water temperature and tidal conditions, as well as other factors.
Controlled depth fishing is practiced with a downrigger 10, seen in FIG. 1 and in detail in FIG. 2. The downrigger typically comprises a housing 12 mounting a reel 14. A boom 16 extends from the housing and has a pulley 18 mounted at its tip. A cable 20 extends from the reel to the pulley and is attached to a weight 22. The weight can vary from 2 to 20 lbs depending on the depth at which the fisherman wishes to troll. A fishing rod holder 24 is typically attached to housing 12 for holding the rod adjacent to downrigger 10. A mounting base 26 is attached to housing 12 and allows the downrigger to be mounted onto a platform, as described below.
As shown in FIG. 1, the downrigger 10 is mounted onto a platform 28 near the gunwale 30 of a fishing boat 32. Typical prior art platforms presently in use are shown in FIG. 3a at 34a and in FIG. 3b at 34b. 
In operation, the fishing line from the rod (not shown) is baited with a lure or bait, and the line is releasably attached to weight 22 via a release mechanism (not shown). Weight 22 is then lowered on cable 20 into the water to the desired depth, the handle of the fishing rod is placed in holder 24, and when trolling, the boat tows the weight through the water, the weight holding the lure at the desired depth. When a fish strikes the lure, the release mechanism releases the fishing line, and the fisherman removes the rod from holder 24 to fight the fish with rod and reel.
As seen in FIGS. 3a, and 3b, the platforms 34a and 34b currently used to mount the downrigger are relatively crude and not easily adaptable to various types of boat hulls, especially with regard to the hull surface angle relative to the boat deck. It is desirable to maintain the mounting base 26 of the downrigger in a substantially horizontal orientation, for example parallel to the boat deck. If the sides of the hull are angled relative to the deck, for example, in a Vee hulled boat, then the prior art platforms shown will not properly support the downrigger base substantially horizontally.
Furthermore, when trolling or fishing in fast running water, relatively large forces are generated putting considerable stress on the boat hull where the platform is attached. If the forces are not properly distributed to the hull, damage can result. This is especially true for small aluminum boats in the 12 to 14 foot range whose hulls are not particularly strong or rigid and, thus, do not inherently provide an adequate mounting point for the prior art platforms. Moreover, the prior art platforms themselves tend to be relatively weak and undesirably flexible, and when such platforms are mounted onto a flimsy boat hull, failure of the entire mounting could occur which would lead to the loss of valuable equipment (rod, reel and downrigger).
Lastly, it is preferable to mount downriggers within the hull so that the downrigger, when rotatably mounted to the platform, can be positioned so that the boom does not extend beyond the hull. This is useful when underway and important for maneuvering the boat near obstacles or docking, as a downrigger extending from the boat may snag on an obstacle, damage other boats or be damaged by contact with a dock or pier.
Clearly, there is a need for a downrigger mounting platform which can be securely mounted to a boat hull and infinitely adjusted to compensate for the relative angle of the hull sides to provide a mounting surface which is substantially horizontal irrespective of the angle of the hull sides. The platform should, furthermore, be strong, relatively rigid and should stiffen the hull and distribute the forces evenly to it. The platform should also enable the downrigger to be positioned entirely within the hull to afford maximum maneuverability to the boat. Lastly, the platform should be easily adaptable to support other equipment, such as fish finders, depth finders or radio equipment and also afford ready access to the equipment mounted thereon.
The universal platform according to the invention is an infinitely adjustable platform which provides a mounting surface adjustable to a substantially horizontal orientation irrespective of the orientation of the surface on which the platform is mounted.
The platform comprises a first plate and a second plate pivotally attached to the first plate. The second plate is rotatable about a first axis mutually parallel to the respective planes of both the first and second plates. Matched lugs extending from the first and second plates rotatably joined by pivot pins provide a convenient means for pivotally attaching the plates.
An elongated support arm is connected between the first and second plates forming a diagonal brace. The first end of the support arm is pivotally attached to the first plate at a first position spaced away from the first axis, the first end being rotatable about a second axis oriented parallel to the first axis. The second end of the support arm is pivotally attached to the second plate at a second position spaced away from the first axis, the second end being rotatable about a third axis also oriented parallel to the first axis.
The support arm has means for adjusting its length arranged between the first and second ends, as well as means for fixing the length of the support arm once the desired length is established.
The first plate is fixedly mountable to a surface such as a boat hull. The first plate is preferably attached to the surface by means of through bolts which engage both the hull and the back plate, although rivets, nails or other fasteners are also useable under appropriate circumstances. The first plate could also be welded or adhesively bonded to the surface.
The second plate is angularly adjustable about the first axis to a substantially horizontal position. The second plate, thus, provides the horizontal mounting surface for a downrigger or other equipment when it is arranged at a predetermined angle relative to the first plate.
In the preferred embodiment, the support arm comprises a first elongated shaft extending from the first end of the arm toward the second end and a second elongated shaft extending from the second end of the arm toward the first end. The shafts engage the means for adjusting the length of the support arm, which comprises a clamping block having first and second side portions arranged opposite each other. The first and second shafts are sandwiched between said first and second side portions of the clamping block. Means for fixing the length of the support arm comprise at least one fastener extending between the first and second side portions for attaching the side portions together and thereby clamping the first and second shafts fixedly therebetween.
The first and second side portions each have a matching through hole aligned substantially perpendicularly to the first and second shafts for accepting the fastener, which comprises a bolt or cap screw and locking nut. The bolt is sized to interengage the through holes in the side portions and bolt the side portions together thereby clamping said first and second shafts therebetween. Preferably the first and second shafts are arranged between the side portions of the clamping block in a parallel, spaced apart relationship. At least one of the first and second shafts has a serrated surface engaging the side portions. The serrated surface increases purchase between the one shaft and the clamping block to provide increased clamping friction for fixing the length of the support arm more securely.
Preferably, the first and second side portions each have a pair of grooves arranged in a parallel, spaced apart relation matched to the spacing of the first and second shafts. The grooves are sized fractionally smaller in diameter than the shafts to frictionally contact the shafts in lengthwise interengagement when the shafts are sandwiched between said first and second side portions. This ensures large clamping forces when the clamping block fasteners are tightened.
It is preferred to construct the platform from durable, lightweight material which is easily worked, such as polycarbonate plastic. Steel or aluminum can also be used if greater strength is required. The material requirements will depend upon the fish being sought and the depth at which trolling will occur. Larger game fish and deeper trolling will require a more robust design using stronger, more durable materials. Hardware such as the attachment bolts, the pivot pins and clamping bolts are preferably stainless steel to prevent corrosion which could be especially troublesome in a salt water environment.
In the preferred embodiment, the attachment of the first plate to the hull should be considered permanent. Preferably, the first plate is relatively stiff and attached with its top portion close to the relatively rigid rail which typically forms the gunwale. The second plate extends downwardly along the hull from the rail, thus, transferring rigidity from the rail area into the otherwise relatively flexible hull. The second plate and the support arm are easily removable when not in use so as not to form an obstruction projecting into the boat.
It is an object of the invention to provide an infinitely adjustable platform which provides a mounting surface adjustable to a substantially horizontal orientation irrespective of the orientation of the surface to which the platform is mounted.
It is an object of the invention to provide a platform for mounting a downrigger to a boat hull which can be infinitely adjusted to compensate for the angle of the hull sides relative to the deck to position the downrigger substantially parallel relative to the deck.
It is another object of the invention to provide a mounting platform which can be securely mounted to a boat hull.
It is yet another object of the invention to provide a mounting platform which is strong, relatively rigid and distributes the forces from trolling evenly to the hull.
It is still another object of the invention to provide a platform which enables the-downrigger to be positioned entirely within the hull to afford maximum maneuverability to the boat.
It is again another object of the invention to provide a platform which will reinforce and stiffen a boat hull to which it is attached.
It is still yet another object of the invention to provide a platform which can be used to mount electronic equipment, such as depth finders, fish finders or radio equipment onto a boat hull.
It is yet again another object of the invention to provide a platform which provides ready access to the equipment mounted thereon.
These and other objects will become apparent from a consideration of the following drawings and detailed description of the preferred embodiment of the invention.